1. Field of the Invention
The present invention relates to a viscous fluid coupling apparatus. The viscous fluid coupling apparatus may be employed as an automobile fan coupling or the like.
2. Description of the Related Art
A conventional automobile fan coupling has suffered from induced rotation of a fan disposed around a housing thereof, because all of the viscous fluid which is sealed in the fan coupling cannot be accommodated in a reservoir chamber of the fan coupling when an engine is stopped, and the viscous fluid remaining in an actuator chamber of the fan coupling consequently transmits torque to the housing of the fan coupling when the engine is started again, thereby causing the induced rotation of the fan.
Accordingly, a viscous fluid coupling apparatus as disclosed in Japanese Unexamined Patent Publication (KOKAI) No. 180727/1988 has been proposed. In this viscous fluid coupling apparatus, in addition to a conventional reservoir chamber, a second reservoir chamber is disposed on a side of an actuator chamber opposite to a side thereof having the conventional reservoir chamber, and the radius of the second reservoir chamber is made identical with the radius of the actuator chamber. With this arrangement, the amount of viscous fluid remaining in the actuator chamber, and immersing a torque transmitter portion of the viscous fluid coupling apparatus, is reduced when an engine is stopped, thereby substantially preventing the induced rotation of a fan from happening at the time of starting the engine.
However, this conventional viscous fluid coupling apparatus has a large axial length because the reservoir chambers are disposed on both sides of the actuator chamber. Consequently, there has arisen a problem that the viscous fluid coupling apparatus having the large axial length cannot be assembled in a space between a front surface of an automobile engine and a rear surface of a radiator where a very small space is usually provided. If the viscous fluid coupling apparatus can be assembled in the small space, the operability of the assembly has been very poor.